Word 2010 document - bizarre behavior

I've never seen anything like this!

Yesterday, I opened a .docx file to format. While scrolling through I noticed that a couple of the sections had only the headings, no body text. When I asked the author of the document, he stated that he had just finished editing it and all of the headings had associated body text. Upon further checking, we noticed that body text (minus any bullet lists) was stripped from the sections and moved further down in the document in an unrelated section (and on one occasion, not in the correct order).

Styles were applied to headings and body text, but not bullet lists. Which leads me to conclude it has something to do with styles - but what?